Geomagnetic disturbances from solar storms or electromagnetic pulse weapons pose a high risk to the electrical power grid. This project examines a real-world example of 3-D mapping of the crust and mantle in the northwestern US from EarthScope data to determine risks posed by ground conductivity that could amplify or change how geomagnetic disturbances affect power lines. This new 3-D method detected surprising effects that the current 1-D method of risk assessment fails to detect.